1. Field of the Invention
The present invention relates to suspensions of mineral fillers, preferably calcium carbonates, and more preferably ground fillers, for example ground calcium carbonates, and additives for producing such suspensions, for example grinding aid agents. The grinding aid agents of the present invention provide suspensions of fillers with improved mechanical properties, particularly the properties of xe2x80x9cstrength at young agesxe2x80x9d of cement matrices or hydraulic binders, or more particularly hydraulic concretes, prepared with these suspensions.
The present invention also relates to mortars, concretes and other compositions based on cement and/or semi-hydrate calcium sulphate, i.e., hydraulic compounds or binders.
2. Discussion of the Background
It is known that cement matrices such as concretes, mortars, grouts, etc, more particularly hydraulic concretes, are used in two main applications: ready-for-use concretes and prefabricated products. In addition, it is known that concrete is composed essentially of a cement and an aggregate as well as water and admixtures or additives.
By granulometry, aggregates are classified into several categories known to those skilled in the art, and defined by the French standard XP P 18-540.
In this standard, the families of aggregates comprise:
O/D fillers, where D less than 2 mm, and at least 70% of the aggregate passes through a 0.063 mm screen,
O/D fine sands, where Dxe2x89xa61 mm, and less than 70% of the aggregate passes through a 0.063 mm screen,
O/D sands, where 1 less than Dxe2x89xa66.3 mm,
gravels, where D greater than 6.3 mm,
d/D fine gravels, where d greater than 1 mm and Dxe2x89xa6125 mm,
d/D ballasts, where d greater than 25 mm and Dxe2x89xa650 mm,
with d and D as defined in this standard.
Such fillers may include ultra-fines which are defined as fillers having a median diameter less than or equal to 20 m measured by means of a Cilas(trademark) 850 or Sedigraph(trademark) 5100 type granulometer (selected according to the granulometry of the filler to be measured). Examples of fillers are, for example, blast furnace cast vitrified slags, fly ash and other additions of silica of high fineness, or calcareous additions such as calcium carbonate.
The incorporation, in cement matrices or hydraulic binders, of fumed silica or siliceous additions, or calcareous additions such as calcium carbonate, is also known. In particular, it is known that calcium carbonate may be used, either as a dispersion in water, or in an aqueous medium without dispersant.
In particular, WO 99/47468 describes the use of calcium carbonate in the form of an aqueous dispersion for preparing concretes. This document is an example of preparing a concrete having a more or less acceptable compromise between ease of handling and resistance to premature aging. However, WO 99/47468 only describes incorporating a dispersant as a liquefier for improving fluidity, which is akin to the known functions of additives in the prior art.
EP 0 271 435, EP 0 725 043 and U.S. Pat. No. 5,614,017 describe the use of plasticizers in cements, which improve the compressive strength, or reduce shrinkage, or increase the workability time, measured with an Abrams cone, also referred to as xe2x80x9cslumpxe2x80x9d. In EP 0 271 435, the additive acts as a water reducer, which is perfectly in accord with the desirability of having a water/cement (W/C) ratio which is as low as possible in order to improve mechanical strength. In EP 0 725 043, the plasticizer is used at a very low concentration and the technical problem posed is completely different from that of the present invention, and as in U.S. Pat. No. 5,614,017. In the three cases, the aggregate is of the O/D filler type (as defined above), the calcium carbonate is used as a dry powder rather than in dispersion, and the addition of the admixture is effected at the time of preparation of the concrete, that is to say subsequent to, rather than before the preparation of the concrete.
It is also known that admixtures can be used for deflocculating the cement paste and/or reducing the quantity of water in the cement. In this regard, it is known that if the proportion of water increases in a cement matrix or hydraulic binder, the mechanical strength is reduced. One of skill in the art, therefore, always endeavours, in their formulations, to reduce the water/cement ratio (W/C). However, one of skill in the art also knows that, if the proportion of water increases in a cement matrix or hydraulic binder, the workability thereof (that is to say its ability to be handled, pumped, etc) increases. Thus, one of skill in the art is therefore very often forced to seek a compromise between the mechanical properties and workability of such cement matrices or hydraulic binders.
One of the most important mechanical properties of cement matrices or hydraulic binders, for one of skill in the art, concerns the xe2x80x9cstrength at young agesxe2x80x9d of the cement matrix or hydraulic binder. This property is defined as the change in the compressive strength curve, according to the age of preparation of the cement matrix or hydraulic binder, in the region of from 0 hours to 7 days following the preparation of the cement matrix or hydraulic binder. Normally, a measurement is made at 2 days and 7 days.
As discussed above, there is an important and recognised need for significantly increasing the strength at young ages property, without negatively affecting other advantageous properties, such as for example workability.
Accordingly, it is an object of the present invention to provide a method of preparing a cement matrix or hydraulic binder comprising adding an aqueous suspension comprising a ground mineral filler and at least one grinding agent to cement or hydraulic binder.
It is yet another object of the present invention to provide a cement matrix or hydraulic binder, prepared by combining a cement or hydraulic binder, and an aqueous suspension comprising at least one ground mineral filler and at least one grinding aid agent.
Thus, in a first embodiment, the present invention provides a method of preparing a cement matrix or hydraulic binder comprising adding an aqueous suspension comprising a ground mineral filler and at least one grinding agent to cement or hydraulic binder. In combination with the other ingredients, the mineral filler and grinding aid greatly increase the mechanical strength, and in particular the strength at young ages, of a cement matrix or hydraulic binder.
The invention therefore relates to a method for conferring on cement matrices or hydraulic binders such as concretes, mortars, grouts or compositions based on calcium sulphate hemihydrate, improved mechanical strength and notably improved mechanical strength at young ages.
The aqueous suspension of ground mineral filler is prepared by the addition of the grinding aid agent or agents to the mineral filler when the mineral filler is ground. In other words, the grinding aid agent or agents are not incorporated directly in the cement matrix or hydraulic binder.
The grinding aid agents of the present invention are natural or synthetic homopolymers and/or copolymers. A copolymer family is described in French patent application No 9905665 of the Applicant, (not published at the time of filing the present application). However, the copolymers described therein have the function of appreciably improving the workability of hydraulic binders. Thus, one of skill in the art would not seek to use such a workability agent as a grinding aid agent in the preparation of a suspension of mineral filler used in the manufacture of cement matrices or hydraulic binders. Likewise, it is not known in the art to prepare a cement matrix by means of suspensions containing at least one grinding aid agent.
Synthetic homopolymers or copolymers may be obtained by the polymerisation of ethylenically unsaturated monomers, by polycondensation, or by ring opening polymerisation.
The polymer or polymers obtained by polycondensation or by ring opening polymerisation comprise polyaspartates and derivatives thereof, or polylactates, as well as water-soluble polyesters, polyamides or polylactones.
The ethylenically unsaturated monomer or monomers may be selected from at least one of the ethylenically unsaturated anionic monomers such as acrylic and/or methacrylic acid, itaconic, crotonic or fumaric acid, maleic anhydride or isocrotonic, aconitic, mesaconic, sinapic, undecylenic or angelic acid, 2-acrylamido-2-methyl-1-propane sulphonic acid, 2-methacrylamido-2-methyl-1-propane sulphonic acid, 3-methacrylamido-2-hydroxy-1-propane sulphonic acid, allylsulphonic acid, methallylsulphonic acid, allyloxybenzene sulphonic acid, methallyloxybenzene sulphonic acid, 2-hydroxy-3-(2-propenyloxy)propane sulphonic acid, 2-methyl-2-propene-1-sulphonic acid, ethylene sulphonic acid, propene suphonic acid, 2-methylpropene sulphonic acid, styrene sulphonic acid, vinyl sulphonic acid, sodium methallylsulphonate, sulphoethyl or sulphopropyl acrylate or methacrylate, sulphomethacrylamide, sulphomethylmethacrylamide, alkylene glycol acrylate or methacrylate phosphate or phosphonate or sulphate or sulphonate, or vinyl phosphonate, or may be selected from at least one non-ionic monomer such as acrylamide or methacrylamide or derivatives thereof, C1 to C40 acrylic or methacrylic acid alkyl-esters, vinyl acetate, vinylpyrrolidone, styrene or xcex1-methylstyrene.
The ethylenically unsaturated monomer or monomers may also be selected from at least one alkoxy-, aryloxy-, alkylaryloxy-, arylalkyloxy-polyalkylene glycol ethylenic urethane monomer, sometimes referred to as special urethane monomer, or an alkoxy-, aryloxy-, alkylaryloxy- or arylalkyloxy-polyalkylene glycol ethylenic ester monomer such as an alkoxy-polyalkylene glycol acrylate, methacrylate or hemimaleate or an oxyalkylated, oxyarylated, oxyarylalkylated or oxyalkylarylated alkoxy-, aryloxy-, alkylaryloxy- or arylalkyloxy-acrylate or methacrylate or hemimaleate (the alkylene, arylene, alkylarylene or arylalkylene oxide number being between 1 and 120), or an alkoxy-, aryloxy-, alkylaryloxy- or arylalkyloxy-polyalkylene glycol ethylenic ether monomer, and optionally one or more ethylenic monomers having at least two polymerizable double bonds, referred to as a cross-linking agents, chosen non-limitatively from the group consisting of ethylene glycol dimethacrylate, divinylacetylene, divinylbenzene, trimethylolpropanetriacrylate, allyl acrylate, methylene-bis-acrylamide, methylene-bis-methacrylamide, tetrallyloxyethane, the triallylcyanurates, allyl ethers obtained from polyols such as pentaerythritol, sorbitol, sucrose or others.
Preferably, the polymers of the present invention are either homopolymers of acrylic or methacrylic acid or the copolymers obtained by the radical copolymerization of at least one anionic monomer with, optionally, at least one alkoxy-, aryloxy-, alkylaryloxy- or arylalkyloxy-polyalkylene glycol ethylenic ester, ether or urethane monomer and more particularly alkoxy-PEG (polyethylene glycol) urethane, and possibly at least one non-ionic monomer in the possible presence of alkoxy-, aryloxy-, alkylaryloxy- or arylalkyloxy-polyalkylene glycol acrylate or methacrylate or hemialeate and more particularly alkoxy-, aryloxy-, alkylaryloxy- or arylalkyloxy-PEG acrylate or methacrylate or hemialeate, the said PEG (polyethylene glycol) having a molecular weight greater than 300, and in the optional presence of ethylenic monomers having at least two polymerizable double bonds, also referred to as cross-linking agents, chosen from the group consisting of ethylene glycol dimethacrylate, divinylacetylene, divinylbenzene, trimethylolpropanetriacrylate, allyl acrylate, methylene-bis-acrylamide, methylene-bis-methacrylamide, tetrallyloxyethane, the triallylcyanurates, allyl ethers obtained from polyols such as pentaerythritol, sorbitol, sucrose or others.
In some cases, the polymers of the present invention may be homopolymers or copolymers or ethylenically unsaturated cationic monomers such as methacrylamido propyl trimethyl ammonium chloride or sulfate, trimethyl ammonium ethyl methacrylate chloride or sulfate, as well as the corresponding quaternized or unquaternized acrylates or acrylamides and/or the dimethyldiallyl ammonium chloride.
The polymer used as a novel agent for improving strength at young ages for cement matrices or hydraulic binders according to the invention is prepared by the known processes of radical polymerization in a solution, in an emulsion, in a suspension or by precipitation of the aforementioned monomer or monomers, in the presence of a catalytic system and known transfer agents, used in appropriate quantities. The molecular weight of the polymer of the present invention may be adjusted by known means such as, for example, adjusting the reaction temperature, the amount of catalyst, the presence or absence of transfer agents, or any other means or combination of means known to one of skill in the polymer synthesis art.
The polymerization catalyst system, which can vary in quantity from 0.1% to 20% by weight with respect to the total weight of monomers, is preferably selected from catalysts which are water-soluble such as, for example, sodium, potassium or ammonium persulphates, azo compounds, or peroxides or hydroperoxides such as, for example, hydrogen peroxide. These catalysts may also be combined with a known reducing compound such as sodium metabisulphite, sodium hypophosphite, phosphorous acid, hypophosphorous acid or metallic salts.
The chain transfer agent is preferably selected from alkyl-mercaptans such as, for example, octanethiol, decanethiol, n-dodecanethiol or t-dodecanethiol or from mercapto-propionic acid, mercapto-succinic acid, thioglycolic acid or mercaptoethanol or secondary alcohols, certain alkyl halides or the salts of phosphorus acids with an oxidation number of less than 5, as well as various other additives, known to one of skill in the polymer art, as a chain limiter.
Throughout the present application, the abbreviations used have the following meaning:
EGMAPO4=ethylene glycol methacrylate phosphate
EGMA=ethylene glycol methacrylate
PEG 350=polyethylene glycol with a molecular weight of 350
PEG 750=polyethylene glycol with a molecular weight of 750
and by analogy any number following the letters PEG indicates the molecular weight of the said PEG.
EA=ethyl acrylate
Acryl=acrylamide
MAA=methacrylic acid
AA=acrylic acid
TEA=triethanolamine
TDI=toluene diisocyanate
IPDI=isophorone diisocyanate
Preferably, the following monomers are polymerized to provide the polymer of the present invention:
a) at least one anionic monomer,
b) optionally at least one non-ionic monomer,
c) optionally at least one alkoxy-, aryloxy-, alkylaryloxy- or arylalkyloxy-polyalkylene glycol ethylenic ester, ether or urethane monomer, sometimes referred to as a special monomer,
d) optionally one of the ethylenic monomers having at least two polymerizable double bonds and referred to as cross-linking agents,
e) optionally at least one cationic monomer.
Even more preferably, the polymer of the present invention is prepared from the following ethylenically unsaturated monomers (% by weight):
a) 2% to 100% of at least one anionic monomer,
b) 0% to 50% of at least one non-ionic monomer,
c) 0% to 95% of at least one alkoxy-, aryloxy-, alkylaryloxy- or arylalkyloxy-polyalkylene glycol ethylenic ester, ether or urethane monomer, sometimes referred to as a special urethane monomer,
d) 0% to 3% of one or more ethylenic monomers having at least two polymerizable double bonds and referred to as cross-linking agents,
e) 0% to 98% of at least one cationic monomer,
the total of monomers a), b), c), d) and e) being equal to 100%.
The preferred anionic monomer or monomers are selected from acrylic acid, methacrylic acid, 2-acrylamido-2-methyl-1-propane sulphonic acid, 2-methacrylamido-2-methyl-1-propane sulphonic acid, 3-methacrylamido-2-hydroxy-1-propane sulphonic acid, allylsulphonic acid, methallylsulphonic acid, allyloxybenzene sulphonic acid, methallyloxybenzene sulphonic acid, 2-hydroxy-3-(2-propenyloxy)propane sulphonic acid, 2-methyl-2-propene-1-sulphonic acid, ethylene sulphonic acid, propene sulphonic acid, 2-methyl propene sulphonic acid, styrene sulphonic acid, vinyl sulphonic acid, sodium methallylsulphonate, sulphopropyl acrylate or methacrylate, sulphomethylacrylamide, sulphomethylmethacrylamide, alkylene glycol acrylate or methacrylate phosphate or phosphonate or sulphate or sulphonate, itaconic acid, maleic anhydride, sodium methallylsulphonate and more particularly chosen from amongst acrylic acid, methacrylic acid, 2-acrylamido-2-methyl-1-propane sulphonic acid, ethylene sulphonic acid, propene sulphonic acid, 2-methylsulphonic acid, ethylene glycol methacrylate phosphate or ethylene glycol acrylate phosphate.
The preferred non-ionic monomer or monomers are selected from acrylamide or methacrylamide or derivatives thereof, the C1 to C40 acrylic or methacrylic acid alkyl-esters, vinyl acetate, vinylpyrrolidone, styrene or xcex1-methylstyrene and more particularly from amongst acrylamide or ethyl acrylate.
The alkoxy-, aryloxy-, alkylaryloxy- or arylalkyloxy-polyalkylene glycol ester monomers are particularly selected from alkoxy-, aryloxy-, alkylaryloxy- or arylalkyloxy-polyalkylene glycol acrylates, methacrylates or hemialeates or an oxyalkylated, oxyarylated, oxyarylalkylated or oxylalkylarylated alkoxy-, aryloxy-, alkylaryloxy- or arylalkyloxy-acrylate or methacrylate (the alkylene, arylene, alkylarylene or arylalkylene oxide number being between 1 and 120).
The alkoxy-, aryloxy-, alkylaryloxy- or arylalkyloxy-polyalkylene glycol urethane monomers are particularly chosen from amongst alkoxy-polyalkylene glycols, reaction products of alkoxy-polyalykylene glycol with a polymerizable unsaturated isocyanate and more particularly from the reaction products of methoxy-PEG with an acrylic, methacrylic, vinyl or allyl isocyanate, wherein the PEG has a molecular weight greater than 300.
The ethylenically unsaturated cationic monomer or monomers are particularly selected from methacrylamido propyl trimethyl ammonium chloride or sulfate, trimethyl ammonium ethyl methacrylate chloride or sulfate, as well as the corresponding quaternized or unquaternized acrylates or acrylamides, and/or the dimethyldiallyl ammonium chloride.
The polymer of the present invention may, subsequent to the polymerization step, be fractionated by any fractionation means known to one of skill in the polymer art.
The polymer of the present invention may be in a completely acidic form, or partially or completely neutralized by one or more neutralization agents having a monovalent function and possibly a polyvalent function. For example, neutralization agents having a monovalent function may be selected from the group consisting of compounds containing alkaline cations, in particular sodium, potassium, lithium, or ammonium, or the primary or secondary aliphatic and/or cyclic amines, such as, for example, ethanolamines, mono- or diethylamine or cyclohexylamine. The neutralization agents having a polyvalent function may be selected from the group consisting of compounds containing divalent alkaline-earth cations, in particular magnesium, calcium, and zinc, and trivalent cations, including, in particular, aluminum, or compounds containing cations with a higher valency.
The mineral fillers of the present invention may be selected, but are not limited to, natural calcium carbonate (chalk, calcite, marble or other natural forms of calcium carbonate), precipitated calcium carbonate, barium carbonate, limy rocks, dolomite, talc, ground silica, silicas in general, fumed silica, fumed titanium dioxide, diatomites, iron oxides, manganese oxides, titanium dioxide, lime, kaolin, metakaolins, clays, mica, plasters, fly ash, slag, calcium sulphate, zeolites, basalt, barium sulphate, aluminum trihydroxide, or mixtures thereof.
The suspension of ground mineral filler of the present invention may be prepared by grinding the mineral filler to be refined in the following manner. First, an aqueous suspension of the mineral matter to be refined is formed, containing the mineral matter and the grinding aid agent or agents. Then the mineral filler is ground with a grinding medium consisting of very fine particles in the aqueous medium containing the grinding aid agent or agents.
In a variant of the method of the present invention, it is possible to prepare a suspension of a mixture of fillers by means of co-grinding the fillers. That is, an aqueous suspension of the mineral fillers to be refined is formed, then the mineral fillers are co-ground. Another method of preparing a suspension of a mixture of fillers according to the present invention comprises grinding each of the fillers separately as described above, and then mixing the suspensions of ground filler material together. The dry weight of the suspension may vary from 10% by weight to 85% by weight.
The ground mineral filler may be ground to the ultrafine stage. In particular, the ground mineral filler may be a calcium carbonate ground to the ultrafine stage, having a median diameter of less than or equal to 20 xcexcm measured by means of a Cilas(trademark) 850 or Sedigraph(trademark) 5100 type granulometer (depending on the granulometry of the filler to be measured).
The grinding aid agent is preferably selected from the polymers, according to the present invention, obtained by radical polymerisation and optionally at least one alkoxy-, aryloxy-, alkylaryloxy- or arylalkyloxy-polyalkylene glycol ethylenic ester, ether or urethane monomer and more particularly alkoxy-polyethylene glycol urethane with at least one anionic monomer, and optionally at least one non-ionic monomer in the possible presence of ethylenic monomers having at least two polymerizable double bonds, also referred to as cross-linking agents.
A second object of the present invention is a suspension of filler or a mixture of fillers comprising a ground mineral filler or fillers as described above, and at least one grinding aid agent as defined above.
A third embodiment of the present invention is a cement matrix or hydraulic binder, such as concrete, mortar, grout, or compositions based on cement and/or calcium sulphate hemihydrate, and more particularly hydraulic concrete, prepared by mixing the cement matrix or hydraulic binder with the aqueous suspension of the ground mineral filler or fillers and at least one grinding aid agent of the present invention. Such cement matrices or hydraulic binders have improved strength at young ages.
The cement matrices or hydraulic binders of the present invention, containing the novel grinding aid agent which improves the strength of the cement matrix or hydraulic binder at young ages, may be used in construction, building, public works, civil engineering, offshore works or as petroleum cements and parapetroleum services.
The invention also covers all embodiments and all applications which will be directly accessible to one of skill in the art, from reading the present application, from his own knowledge, and possibly from simple, routine tests.
Having generally described this invention, a further understanding can be obtained by reference to certain specific examples which are provided herein for purposes of illustration only, and are not intended to be limiting unless otherwise specified.